因为an是等差数列,设公差为d.已知:a1+a4+a7+……+a97=10
a2+a5+a8+……+a98=20
(a1+d)+(a4+d)+……+(a97+d)=20
a1+a4+……+a97+33d=20
10+33d=20
33d=10
a3+a6+a9+...+a99
=(a2+d)+(a5+d)+(a8+d)+……+(a98+d)
=a2+a5+a8+……+a98+33d
=20+10
=30
因为an是等差数列,设公差为d.已知:a1+a4+a7+……+a97=10
a2+a5+a8+……+a98=20
(a1+d)+(a4+d)+……+(a97+d)=20
a1+a4+……+a97+33d=20
10+33d=20
33d=10
a3+a6+a9+...+a99
=(a2+d)+(a5+d)+(a8+d)+……+(a98+d)
=a2+a5+a8+……+a98+33d
=20+10
=30